The present invention relates to information reproducing apparatuses for reproducing information of a recording medium having records with extreme density and, more particularly, to an information reproducing apparatus adapted for reproduction by a light in a near field.
In many of the existing information reproducing devices, reproduction is implemented for the information recorded of an optical disk of an exclusive reproduction type represented by CDs and CD-ROMS. For example, the CD is recorded, as convex/concave information, with pits that has a size of nearly a wavelength of a laser light to be used upon reproduction and a depth of nearly a quarter of the wavelength. To reproduce the information, light interference phenomenon is utilized. When a laser light spot is illuminated onto a pit, there occurs due to the pit depth of a quarter wavelength a optical-path difference of a half wavelength of the illuminated laser light between a reflected light reflected upon a bottom surface of the pit and a reflected light reflected upon a surface outside the pit. The reflected light obtained however is weakened as compared to a case a laser light spot is illuminated on the surface outside the pit. In this manner, the presence and absence is determined due to detection of an intensity of a reflected light, thus achieving reproduction of information recorded on the optical disk.
The above reflected light detection system uses a lens optical system employed in the conventional optical microscope so that the laser light spot size cannot be reduced smaller than a half wavelength due to a diffraction limit of light. Consequently, where further increasing the information recording density on the optical disk, the size and truck pitch of pits are decreased to reduce the information recording unit down to a size smaller than a laser light wavelength. The conventional information reproducing apparatus cannot cope with information reproduction from such an optical disk.
Meanwhile, there is known a near-field optical microscope which uses a probe having a microscopic aperture with a diameter smaller than a wavelength of a laser light to be illuminated, say approximately one-tenth thereof, to utilize a near-field light (evanescent field) and thereby observe a microscopic surface structure of a sample. As one of near-field utilization schemes of the near-field optical microscopes, there is a method that a microscopic aperture of a probe and a sample surface are brought into proximity to a distance of nearly the microscopic aperture of a probe so that a transmission light can be illuminated from a sample backside to cause a near-field light on the sample surface to be observed by transmission through the probe. In this case, the near-field light caused in the sample surface involves an intensity and phase reflecting a fine structure on the sample surface. This near-field light is extracted as a propagating light through the microscopic aperture of a probe and then detected by a photo detector, thus achieving observation with a resolution unrealizable by the conventional optical microscopes.
Accordingly, by the utilization of the above near-field optical microscope technology, it is possible to reproduce even an information record unit recorded more microscopically than a recording density on the conventional information recording medium represented by the CD.
However, the near-field light generated by light illumination is very weak. Furthermore, because the probe is added therein with illumination light or stray light such as scattering light, it has been difficult to detect the presence or absence of a pit with sufficient intensity and preferred S/N ratio.
Also, in the case that the illumination light to an optical disk is intensified in order to cause an intensified near-field light, heated are not only a pit portion but also a probe tip positioned nearby the pit portion. There is a possibility that an optical disk or probe be damaged or deformed.
Therefore it is an object of the present invention to provide, in view of the above-stated problems, a near-field optical head for realizing with reliability information reproduction of an optical disk having records with extreme density.
In order to achieve the above object, a near-field optical head according to the present invention is a near-field optical head for reproducing information on a recording medium that is formed on an electrode and emits light by applying an electric field, the near-field optical head comprising; a slider having at least one hole formed through in an inverted cone form such that a summit thereof is rendered as a microscopic aperture and a head electrode opposed to the electrode and provided in the inverted cone formed hole; a light detecting element arranged in the slider on an opposite surface to a surface formed with the microscopic aperture in a manner corresponding to the microscopic aperture; the microscopic aperture and the recording medium being brought into proximity; and a voltage being applied to between the electrode and the head electrode.
Accordingly, the head electrode can apply an electric field only to a microscopic region of the recording medium, thereby causing light emission. Also, the emitted light is scattered by a microscopic aperture in proximity to the recording medium, and propagated to the light detecting element and thereafter received by the light detecting element, thereby receiving the light emitted only by the microscopic region of the recording medium. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density.
Also, a near-field optical head according to the invention is a near-field optical head for reproducing information. on a recording medium that is formed on an electrode and emits light by applying an electric field, the near-field optical head comprising: a slider having at least one hole formed through in an inverted cone form such that a summit thereof is rendered as a microscopic aperture; a microscopic electrode formed on a side surface of the inverted cone formed hole; a light detecting element arranged in the slider on an opposite surface to a surface formed with the microscopic aperture in a manner corresponding to the microscopic aperture; the microscopic aperture and the recording medium being brought into proximity; and a voltage being applied to between the electrode and the microscopic electrode.
Accordingly, the microscopic electrode can apply an electric field only to a microscopic region of the recording medium, thereby-causing light emission. Also, the emitted light is scattered by a microscopic aperture in proximity to the recording medium, and propagated to the light detecting element and thereafter received by the light detecting element, thereby receiving the light emitted only by the microscopic region of the recording medium. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density.
Also, a near-field optical head according to the invention is a near-field optical head for reproducing information on a recording medium that is formed on an electrode and emits light by applying an electric field, the near-field optical head comprising: a slider having at least one hole formed through in an inverted cone form such that a summit thereof is rendered as a microscopic aperture; an optical waveguide formed on a side surface of the inverted cone formed hole; a tip sharpened electrode formed inside of the inverted cone formed hole and having a tip directed to the microscopic aperture; a light detecting element arranged in the slider on an opposite surface to a surface formed with the microscopic aperture in a manner corresponding to the optical waveguide; the microscopic aperture and the recording medium being brought into proximity; and a voltage being applied to between the electrode and the tip sharpened electrode.
Accordingly, the tip sharpened electrode can apply an electric field only to a microscopic region of the recording medium, thereby causing light emission. Also, the emitted light is scattered by a microscopic aperture in proximity to the recording medium, and propagated through the optical waveguide and thereafter received by the light detecting element, thereby receiving the light emitted only by the microscopic region of the recording medium. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density and is compact in structure.
Also, a near-field optical head is a near-field optical head for reproducing information on a recording medium that is formed on an electrode and emits light by applying an electric field, the near-field optical head comprising: a slider having at least one protrusion formed in an inverted cone form such that a summit thereof is opposed to the recording medium; a microscopic electrode formed on a side surface of the protrusion such that a microscopic aperture is formed at a tip; a light detecting element arranged in the slider on an opposite surface to a surface formed with the protrusion in a manner corresponding to the protrusion; the protrusion and the recording medium being brought into proximity; and a voltage being applied to between the electrode and the microscopic electrode.
Accordingly, the microscopic electrode can apply an electric field only to a microscopic region of the recording medium, thereby causing light emission. Also, the emitted light is scattered by a microscopic aperture in proximity to the recording medium, and received by the light detecting element, thereby receiving the light emitted only by the microscopic region of the recording medium. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density and is compact in structure.
Also, a near-field optical head according to the invention is a near-field optical head for reproducing information on a recording medium that is formed on an electrode and emits light by applying an electric field, the near-field optical head comprising: a slider having at least one protrusion formed in an inverted cone form such that a summit thereof is opposed to the recording medium; a microscopic electrode formed at a tip of the inverted cone form; a light detecting element arranged in the slider on an opposite surface to a surface formed with the protrusion in a manner corresponding to the protrusion; the protrusion and the recording medium being brought into proximity; and a voltage being applied to between the electrode and the microscopic electrode.
Accordingly, the microscopic electrode can apply an electric field only to a microscopic region of the recording medium, thereby causing light emission. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density and is compact in structure.
Also, a reproducing method according to the invention is a reproducing method for reproducing information on a recording medium that is formed on an electrode and emits light by applying an electric field, the reproducing method comprising: using a near-field optical head having a slider opposed to the electrode and formed with at least one tip sharpened head electrode, and a light detecting element arranged in the slider in a manner corresponding to the head electrode; bringing the protrusion and the recording medium into proximity; applying a voltage to between the electrode and the head electrode to cause the recording medium to emit light; and detecting a light due to light emission by the light detecting element.
Accordingly, the head electrode can apply an electric field only to a microscopic region of the recording medium, thereby causing light emission. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density.
Also, a reproducing method according to the invention is a reproducing method for reproducing information on a recording medium formed on an electrode and emits light by applying an electric field, the reproducing method comprising: using a near-field optical head having a slider formed with at least one microscopic aperture and having a head electrode opposed to the electrode and provided in the vicinity of the microscopic aperture, and a light detecting element arranged in the slider on a opposite surface to a surface formed with the microscopic aperture in a manner corresponding to the microscopic aperture; bringing the microscopic aperture and the recording medium into proximity; applying a voltage to between the electrode and the head electrode to cause the recording medium to emit light; and detecting a light due to light emission by the light detecting element through the microscopic aperture.
Accordingly, the head electrode can apply an electric field only to a microscopic region of the recording medium, thereby causing light emission. Also, the emitted light is scattered by a microscopic aperture in proximity to the recording medium, and propagated to the light detecting element and thereafter received by the light detecting element, thereby receiving the light emitted only by the microscopic region of the recording medium. As a result, it is possible to provide a near-field optical head which can reproduce, with high S/N, information recorded with extreme density.